Mixtures

 

Mixtures Infographic

All of us realize we are surrounded by “stuff” or more precisely, matter. But getting a handle on the various types of matter around us is a different story. It is a little like walking down a shopping mall with stores that have no store signs labeling what kind of goods they sell. All you can do is look through the windows to get an idea of what they offer for sale.

To sort out the kinds of stuff that surround us, chemists look at the physical and chemical properties of matter and classify it in to various groups.

One of the largest distinctions is between pure substances and mixtures. Pure substances (or just substances) are homogeneous (that is, the same throughout) and have a definite composition, which means they have simple whole number ratios (by mass) between elements that make them up. These are the elements (like gold or carbon) and compounds,(like salt or calcium carbonate) that we tend to spend a lot of time studying in chemistry, because they are the building blocks for all the other types of matter we encounter.

Mixtures on the other hand are a bit messier. They are combinations of two or more materials. This means mixtures can usually be separated back into their original materials by physical processes. A good non-chemical example of a mixture is a jar of mixed nuts, or a drawer with miscellaneous kinds of screws, bolts and washers.

Solutions, suspensions and colloids are similar in that they are combinations of smaller amounts of solute in larger amounts of solvent. The main reason for the varying characteristics among them is the particle size of the solutes.

Emulsions are a special case. An emulsion can be made with two liquids that would normally not mix, such as oil and water. In the case of mayonnaise an egg yolk, which contains the emulsifier lecithin, is used to suspend the oil in tiny droplets. The lecithin coats the oil droplets so its “fat loving” side is on the inside with the fat, while the “water loving” side faces the aqueous solvent side.

Although solutions are often introduced with examples such as sugar dissolving in a pitcher of water for Kool-Aid, solute-solvent relationships can involve various phases beyond solids in liquids.

Air is a common example of a gas-gas solution and soda is carbon dioxide gas dissolved in liquid water. Hydrogen gas can dissolve in palladium metal as an example of gas-solid solutions. You might be wearing a solid-solid solution right now in the form of alloy metals used in jewelry. Similar phase combinations occur in suspensions and colloids. A nice challenge would be to come up with other everyday examples of various phases in solutions, suspensions, colloids or other mixtures.

Finding other examples could help sort out the messy mix of mixtures that surround us!

This graphic is a winning entry in the 2015-2016 ACS ChemClubs/ChemMatters Infographic Contest. Students, teachers, and other chem enthusiasts were challenged to take a chemistry topic and turn it into an original informational graphic. Entries were judged on originality, and the ability to convey accurate science details clearly and creatively. This infographic was conceived by Aaron Herrera and Emerald Rawls from Mapleton Expeditionary School of the Arts in Thornton, CO.

Chemistry Contests at Enrico Fermi High School

Two students from the Enrico Fermi High School ChemClub in Enfield, Connecticut, recently stepped up to organize several contests for our Club. They took care of the organizing, and it has worked out great. The best three were:

  • A contest to see who could launch a hydrogen–oxygen disposable pipet bulb rocket the furthest. Directions to make these rockets are online, such as “Micro-Rocket Challenge.”
  • A contest for making the best smoke bomb (small scale of course). You can make your own with directions online.
  • The last one was making rainbows preparing extracts from fruits and vegetables, then adding acids and bases. The photo shows the winning rainbow. The activity was based on the April 2013 article “Plant Pigment Identification: A Classroom and Outreach Activity” by Garber, Odendaal, & Carlson in the Journal of Chemical Education. The activity uses items from the grocery store like red cabbage, radishes, cranberries, concord grape juice, and blackberries.

test tubes with filled with various colored liquids

Chemists Celebrate Earth Day – April 22, 2014

Help your ChemClub to be Earth Advocates!

CCED

Chemists Celebrate Earth Day (CCED) is an annual celebration that  brings a focus to environmental causes, such as clean air, water, and energy in the context of basic chemistry. The American Chemical Society (ACS) offers events, contests, and educational resources for members, chemical educators, and chemistry enthusiasts to illustrate the positive role that chemistry plays in preserving the Earth.   The CCED 2014 theme is the “Wonders of Water”, exploring the unique properties of water that are crucial for life and a cleaner environment.

There are a number of great resources available for your celebration of Earth Day.  This is a great opportunity to show how chemistry works in everyday life.  It is also a chance to demonstrate how central chemistry is in many environmental issues.  One great place to start is with the materials in the ChemClub 2013-2014 Resource Packet #3, which includes demonstrations, lab-based activities, and activities for outside the lab.  Each resource packet also includes a table categorizing these demos and activities according to common high school chemistry curriculum topics.  You will also see sample Club meeting guides and a copy of ChemMatters magazine, which features articles dealing with environmental issues.

At the CCED web site there are more resources of interest.

CCED Illustrated Poem ContestPoetry contest graphic

As part of CCED activities, the ACS is sponsoring an illustrated poem contest for students in Kindergarten – 12th grade. Tap into your creative side and submit a poem.  Entries will be judged based on relevance to and incorporation of the CCED theme (“The Wonders of Water”), word choice and imagery, colorful artwork, adherence to poem style, originality and creativity, and overall presentation. The poems can be in any of seven styles, from haiku to free verse and must be less than 40 words long.

Celebrating Chemistry

This publication is aimed at younger students and is perfect for any outreach your club might do with elementary school-age kids.  This year’s issue includes stories on how soaps work, why oil and water don’t mix and explores aquifers. Celebrating Chemistry is available in both English and Spanish versions.

CCED Education Resources

Find a number of helpful resources to aid your CCED activities.  Some of the resources include links to the Journal of Chemical Education, ACS CCED promotional products, web seminars, podcasts and much more.

CCED Community Events

Discover local events happening in your area that you may want to join.  It also has suggestions for organizing your own community event, if that is something you and your club would like to take on.

As you can see there are lots of resources for Chemists Celebrate Earth Day.  Now all that is left is for you to make a plan.  Do something grand, or something at a smaller scale, on Earth Day April 22, 2014.

Canoeing on Deep River

 

 

Stories of Chemistry

(Part 4 of 4 - Photography Contest Entries)

Let us know which of these pictures from the ChemClub Photography Contest are your favorites. The photo with the most likes, comments, etc. will be the ChemClub Choice Award winner!

Stories of Chemistry

For the stories of chemistry category, students were to communicate chemistry in a photojournalistic style using a series of photos with a story about the photo’s relationship to chemistry.

Titration is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of a known reactant. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the titrant or titrator, of a known concentration (a standard solution) and volume is used to react with a solution of the analye or titrnad, whose concentration is not known. Using a calibrated burette or chemistry pipetting syringe to add the titrant, it is possible to determine the exact amount that has been consumed when the endpoint is reached. The endpoint is the point at which the titration is complete, as determined by an indicator. This is ideally the same volume as the equivalence point – the volume of added titrant at which the number of moles of titrant is equal to the number of moles of analyte, or some multiple thereof. In the classic strong acid-strong base titration, the endpoint of a titration is the point at which the pH of the reactant is just about equal to 7, and often when the solution takes on a persisting solid color as in the pink of phenolphthalein indicator.

Colors of Chemistry

(Part 3 of 4 - Photography Contest Entries)

Let us know which of these pictures from the ChemClub Photography Contest are your favorites. The photo with the most likes, comments, etc. will be the ChemClub Choice Award winner!

Colors of Chemistry

The pictures in this category show how chemistry contributes to colors of things in the world around you. Information about each entry is below the photo. When leaving a comment about a certain picture use the title found above the photo.